1. Field of the Invention
This invention generally pertains to emergency breathing devices, and specifically to devices for breathing by persons buried in snow.
2. Description of Related Art
Avalanches are the chief causes of snow burial. Such burials kill many highway and railroad workers, backcountry skiers and snowshoers, and mountain residents each year. Annual avalanche mortality estimates have been 35-40 persons in Switzerland, about the same number in Austria, 31 in France, about 30 in Japan, 20-30 in Italy, 17 in the United States, 10-15 in Norway, about 10 in Germany, and 7 in Canada. In a 1994 article in the journal Nature, Falk et al. still estimated 150 avalanche deaths annually in the Alps. Colorado has the most avalanche deaths among American states. About 500 persons have died in Colorado avalanches, and in the heavy snows of 1992-1993 Colorado recorded 12 avalanche deaths.
An additional hazard for snow burial is the collapse of "tree wells", which are steep-sided pits of snow around coniferous trees. Skiers sometimes fall into tree wells as they pass a tree, and the collapsing snow then covers the person.
Of persons totally buried in snow with no tell-tale sign to the surface such as a protruding ski, three out of four will not survive. About one-third of avalanche victims die from the trauma of being dragged into trees or rocks. The rest die of suffocation beneath the snow. Suffocation is quick; only 30 percent survive 35 minutes'burial. In their 1994 article in Nature, Falk et al. call for the development of ". . .self-help techniques to facilitate creation of a life-saving air pocket, which would give the skier a relatively safe haven . . ."
Many emergency breathing devices aim to remedy polluted or oxygen-deficient air, such as smoky buildings or methane-filled mines. Others address surroundings with little or no breathable air, such as high-altitude or underwater conditions. Approaches include various combinations of filtering pollutants from incoming air, supplying fresh oxygen from chemical or compressed-gas sources, or rebreathing of expired air, sometimes after removal of carbon dioxide. U.S. Pat. No. 4,019,507issued to Oetjen et al in 1977 describes an example of a filtering device; it filters incoming air and mixes it with chemically-supplied oxygen. Similarly, U.S. Pat. Nos. 5,036,842 to van der Smissen et al. in 1991 and 5,065,745 to Meier in 1991 use motorized blowers to move polluted air through filters. But such heavy, mechanized devices are impractical for wilderness skiers and snowshoe enthusiasts, who constantly must carry all of their equipment on their backs.
Various patents describe emergency breathing devices containing oxygen sources. U.S. Pat. No. 439,093 issued to Barian in 1890 used a simple sealed bag to hold a supply of air at standard pressure. Others describe air or oxygen supplies in compressed-gas cylinders. The later include these U.S. Pat. Nos. 3,762,407 issued to Shonerd in 1973; 4,802,472 to Jung in 1989; 4,821,712 to Gosset in 1989; 4,887,591 to Okumura in 1989; 4,960,120 to Constance-Hughes in 1990; 4,996,982 to Williamson in 1991; and 5,099,835 to Nelepka in 1992. But before rescue an avalanche victim may be buried for some minutes to several hours. Large compressed-gas cylinders are too heavy to be carried by skiers, and small ones may be emptied before rescue occurs. Moreover, some 50-95 percent of snow's volume is air, pollutant-free and needing no filtering. Devices with self-contained oxygen sources obviously do not utilize that air in the snow.
U.S. Pat. No. 1,814,506 issued to Davis in 1929 extended the duration of air supply through rebreathing. The person extracts more oxygen from the air by rebreathing expired air after chemicals remove carbon dioxide. U.S. Pat. No. 2,852,023 issued to Hamilton et al in 1958 0added a compressed gas supply to replenish oxygen in rebreathed air. Further refinements were offered by these U.S. Pat. Nos. 3,976,063 issued to Henneman et al in 1976; 4,163,448 to Grouard in 1979; 4,794,923 to Bartos in 1989; 4,917,081 to Bartos in 1990; 4,938,211 to Takahashi et al in 1990; 4,964,404 to Stone in 1990; 4,964,405 to Amoth in 1990; 5,036,841 to Hamilton in 1991; and 5,027,810 to Patureau et al in 1991. But clean air is plentifully available in snow; it need not be rebreathed. And the weight and mechanical complexity of these rebreathing devices, which may be excellent for fireman or miners, make them impractical for wilderness skiers.
Neither are the skier's problems of weight, size, and mechanical complexity solved by chemically-generated oxygen supplies. Examples of the latter appear in these U.S. Pat Nos. 2,444,029 issued to Bowen in 1948; 4,164,218 to Martin in 1979; and 4,840,170 to Dahrendorf et al in 1989. The self-contained chemical oxygen supply is heavy, and the considerable heat produced in these exothermic reactions might burn the buried, immobile avalanche victim.
All of the above devices were designed for firemen, miners, aviators, and other non-skiers. U.S. Pat. No. 4,365,628, issued in 1982 to Hodel, described an emergency-breathing device with many of the above features for avalanche victims. Skiers would wear this device, with its compressed gas supply, carbon-dioxide scrubber, and spring-loaded valves, on a vest. It did not utilize the air contained in snow. It was too heavy and complex to find wide use.
Although appropriate for brief use by miners, fireman, aviators, etc., the above emergency breathing devices have major disadvantages for backcountry skiers, snowshoe travellers, ski patrol workers, and others exposed to avalanche hazards:
First, devices with filters, oxygen canisters, pressure valves, chemical supplies of oxygen, etc., are unacceptably heavy for backcountry travellers. Miners and others may stow emergency breathing equipment in convenient places, donning the equipment only in an emergency. Thus, within reason weight is a minor consideration for them. But for backcountry travel a skier must constantly carry the breathing equipment, together with food, sleeping bags, and other gear. So light weight is crucial for avalanche breathing devices.
Second, many previous devices require too much time to don or activate. Avalanche breathing devices must be instantly usable. Skiers frequently are swept away without warning. The victim must begin using the device before the snow stops moving, often in a very few seconds, because most victims are immobilized by the packed snow once sliding ends.
Third, even seemingly simple procedures for activating previous devices may be much too complex for the panicked avalanche victim suddenly being swept along under moving snow. The victim, perhaps still attached to backpack, skis, and ski-poles, could follow only the very simplest of activating procedures.
Fourth, all previous emergency breathing devices depended on air supplied from the device itself, or on filtered atmospheric air. Pressurized cannisters of air or oxygen are too heavy to be carried by backcountry skiers, and atmospheric air is not directly available to the buried person. But virtually limitless quantities of unpolluted air in need of no filtering can slowly flow through snow itself. Failure to use that air because of reliance on other sources adds great complexity, risk of mechanical failure, and weight to the breathing device.
Accordingly, several objects and advantages of the present invention are: First, it is a very light, easily carried, breathing device. Second, it can be activated essentially instantly. Third, its activation procedure is so simple that even a severely panicked victim can use it. Fourth, it extracts air from snow, providing an air supply even if rescue requires many minutes to a few hours.
Further objects and advantages of the present device are that, first, it is made of widely-available and inexpensive materials. It is assembled easily. The device can be packaged for sale from sporting-goods and outdoor-gear shops. It can be manufactured and sold at a price acceptable to outdoor sportspersons, ski patrol groups, and other probable users. Still further objects and advantages will become apparent from consideration of the ensuing description and drawings.